1. Field of the Invention
The present invention relates to a method of producing a plurality of labels located consecutively on a web. Each label includes a respective circuit of an inductive and at least one capacitive element, thus forming an oscillatory circuit, and including further an insulating support on one side of which said inductive element formed of flat electrical conductors and the one surface of said capacitive element connected thereto are located in accordance with a predetermined pattern. The counter surface of said capacitive element is located at the reverse side of said insulating support and is electrically connected to the electrical circuit at the front side. The invention relates further to labels produced in accordance with above method. The invention relates also to a controlling and safeguarding system including labels produced in accordance with the method.
The present invention relates more specifically to a novel method of producing labels equipped with electrical oscillating circuits, such as labels used in specific applications of a great variety of branches of industry. Such labels incorporating oscillating circuits are used, for example, for monitoring and recognizing moving objects while possibly emitted signals serve for triggering of further method steps. A specific application of such labels is to be found in so-called article controlling and safeguarding system.
A decisive matter regarding such applications is that such oscillating circuits can be obtained at low costs and further and still more important, that they incorporate a high stability of the frequency and quality of the coils in order to avoid erroneous detections with a high probability.
2. Description of the Prior Art
Such labels having oscillating circuits are currently widely used. They are produced by many different methods. Generally, the starting material is a carrier made of an electrically non-conductive material while a conductive foil is placed on its front as well as on its reverse side. The desired conductors for the forming of the inductive and the capacitive elements are then formed out of these foils. This is made generally by specific etching methods, but other methods have, however, also been suggested, such as stamping or punching or use of laser rays.
It has been mentioned above that a broad application of such labels incorporating oscillating circuits is possible only if they can be manufactured with a maximal precision, and also at low costs. The necessary series production of such articles has hitherto met with large obstacles, specifically with regard to the demands of precision.